The present invention refers to a cutting tool for chip removing machining.
Such a cutting tool typically includes a holder body with a cutting insert receiving site including a base surface and side supporting means. A cutting insert is located in the cutting insert receiving site and is supported by the base surface and side supporting means. A locking pin is detachably connectable to the holder body in the area of the cutting insert receiving site. The locking pin is axially displaceable relative to the holder body and has a longitudinal center axis diverging away from the side supporting means as it progresses upwardly. The cutting insert has a fixing hole extending through the insert, and the locking pin has a head insertable into the fixing hole. The design of the head and the fixing hole and the inclination of the longitudinal center axis are so mutually adapted to each other that, in an active position of the locking pin, a lower contact portion of the head engages the inner portion of the fixing hole and an upper contact portion of the head engages the outer portion of the fixing hole. Those contact portions are located on opposite sides of the head of the locking pin.
In an inactive position of the locking pin, i.e., the locking pin being displaced axially away from the base surface by a limited distance, the cutting insert can be mounted in or removed from the cutting insert receiving site. That is, it is unnecessary to completely detach the locking pin from the holder in order to exchange cutting inserts.
Cutting tools of the above-mentioned type previously known, see U.S. Pat. Nos. 3,740,807 and 3,913,197.
In the arrangement shown in U.S. Pat. No. 3,740,807 the cutting insert has a cylindrical hole and the longitudinally spaced portions of the locking screw that engage the hole are frusto-conical with decreasing cross-sections in opposite directions. By studying FIG. 2 of that patent, one can see that a lifting force applied to the cutting insert will be counteracted only by friction forces between the locking screw and the hole of the cutting insert.
In the arrangement shown in U.S. Pat. No. 3,913,197, the cutting insert has a hole including two frusto-conical sections converging at the center of the insert. The locking screw is generally of the same design as the locking screw of U.S. Pat. No. 3,740,807. However, when the locking screw engages the upper frusto-conical section of the hole of the cutting insert, a locking force which prevents lifting of the insert will be imposed.
The present invention is primarily related to a cutting tool including a cutting insert having a fixing hole of a standardized configuration, i.e., a hole defined by ISO No. 6987 wherein a lower end of the hole (i.e., an end disposed closest to the base surface of the insert receiving site) is generally cylindrical and adjoins a generally tapered portion thereabove which is of gradually enlarging cross-section in an upward direction. The taper of the tapered portion is to be designed for use with a countersunk head screw having a head taper angle between 40.degree. and 60.degree.. A locking screw according to combination with a hole conforming to ISO 6987, due to the fact that the upper contact portion of the locking screw has a decreasing cross-section towards the upper end of the head of the locking screw. As a result, when using cutting inserts having a through-hole conforming to ISO 6987, it has been heretofore necessary to completely detach the locking pin from the holder in order to exchange inserts.
An object of the present invention is to present a cutting tool having a simple but reliable locking arrangement for a cutting insert having a hole according to ISO 6987 or a similar design, wherein the cutting inserts can be exchanged without completely removing the locking pin from the holder.